(a) Field of the Invention
This invention generally relates to a safety hook and attachment system for connecting the safety hook to a harness.
More particularly, but not by way of limitation, to a hook with a gate that prevents unwanted release of the hook and allows the gate to cooperate with the hook in a synergistic manner.
(b) Discussion of Known Art
There is a large variety of safety hooks or “tie back” snap hooks that are designed for use as safety equipment. These hooks typically include a J-shaped hook portion that includes a gate that closes the mouth of the hook in order to prevent the inadvertent release of the hook.
The primary purpose of these hooks is to tether a worker to a support structure in order to prevent an unrestrained fall to the ground. The safety hooks are typically used as part of a lanyard that includes a shock absorber or dampening mechanism. One end of the lanyard is attached by way of a safety hook to the back of a harness, while the other end of the lanyard is attached to some sort of support structure, such as a crane, a section of steel or rebar, or other attachment point specifically provided for restraining a fall.
Because of the variety of attachment points and work condition present during an instance where the safety hook and fall arrest systems must be deployed, the actual fall path and restrain conditions are rather unpredictable. Thus, the loading on a safety hook can vary depending on what occurs during the fall. For example, some fall conditions can cause the entire load from the fall to be reacted on the gate of the hook, which is typically the weakest portion of the hook. In order to ensure that the gate does not fail, safety hooks must have gates that are capable of resisting the loads from the fall without opening into or out of the mouth of the hook.
Thus, the safety hooks, also referred to as tie back snap hooks, are frequently used in personal fall protection applications where anchorage connectors are not readily available. A tie back snap enables a worker to loop the lanyard that is connected to the snap around a pipe or beam and then snap it back onto itself. This enables the worker to use items such as pipes in a pipe rack or I-beams and other structures in building steel as anchorage tie off points where no other types of anchorage connections exists. Currently tie back applications are performed in two ways. In the first a D-ring is attached to the lanyard with a slip buckle that is positioned halfway between the snap end and the shock absorber end of the lanyard. The worker can then loop the lanyard over a pipe or beam and connect the snap into the D-ring. The D-ring location is then adjusted to provide a snug fit around the pipe or beam. With this application a standard double action single locking snap can be used to create a tie back application. In the second application the lanyard is looped over the pipe or beam and then the snap is connected or snapped back around the lanyard itself This type of application has several inherent problems.
The first problem is that the lanyard webbing can lie across the inside of the snap gate. In a fall arrest the lanyard tension could put as much as 5000-lb. of load on the snap gate. Standard snap gates are designed according to OSHA regulation to withstand only a 350-lb. load. Therefore standard, double action, single locking snaps will not work for this type of application. Another danger with the use of snap hooks is that a snap, when looped over an I-beam with the edge of the gate against the flange of the I-beam, can fail by forces on the gate which can open by the due to the action of the I-beam pressing against the gate during fall arrest. For these reasons tie back snaps must be designed so that the gate will take a 5000-lb. load without failure in any direction, not the 350-lb. load typical in standard locking snap hooks. Some manufacturers have designed snap hooks that meet these requirements. Typically these snaps are much larger, must have forged rather than stamped steel gates, and must use much larger and stronger hinge pins. All of which adds greatly to the cost and weight of the product.